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Development of a murine model of actinobacillus actinomycetemcomitans-induced pathogenesis Colfer, Ellen Lee

Abstract

Animals have been used in health sciences for over 100 years to study the mechanism and virulence of bacterial pathogens. Many variations of the abscess model of inflammation have been developed but they do not provide the ability to easily quantify the resulting pathology. The aims of this study were to 1) develop a quantitative method of grading an inflammatory response to Actinobacillus actinomycetemcomitans-mduc&d (A. actinomycetemcomitans) inflammation using non-viable bacteria, 2) determine the reproducibility of the inflammatory and immunohistologic response and 3) determine the virulence of three strains of A. actinomycetemcomitans using the proposed grading system developed in the model. During the study, CD-I mice were injected s.c. in the ear and/or abdomen with two serotypes strains (three strains) of A. actinomycetemcomitans bacteria, JP2 (serotype b), ATCC 43718-Y4 (serotype b) and IDH 1705 (serotype e). Two grading systems were proposed for histological and immunohistological evaluation of the tissues. The histological evaluation was based on the area of the inflammatory spread within the tissues and number of inflammatory cells counted using an optic grid. The immunohistologic response was determined for the three antibodies; F4/80 antimonocyte/ macrophage antibody, anti-neutrophil antibody and anti-CD3 T cell antibody, by the number of cells found in the tissues. The reproducibility of the kinetic study was deterirrined by nonparametric analysis of variance using the Kolmogorov-Smirnov statistic. The results of the study did revealed that non-viable A. actinomycetemcomitans could elicit both an inflammatory and an immunohistologic response. The quantitative analysis for both the Histologic Score and the Immunohistologic Score suggested that there was a difference in virulence between the strains that was also dependent on dose (dilution) and time. The results demonstrated a strong trend towards a graded virulence and immunological responses of JP2 ≥Y4 ≥IDH 1705.

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